This invention pertains to recording instrument marking pens and particularly to disposable markers for such pens, which markers are adapted to pass in close proximity to adjacent pens and to lay down a constant width trace notwithstanding the close proximity passage.
Recording instruments utilize a wide variety of pen designs and markers, such as "bucket" pens, "V" pens and pens with tubular stylii. Often an instrument includes two or more pens which must produce close proximity tracing. But the nature of these pen marker tips does not allow the desired closeness of passage of adjacent tips. Thus, there has been a need in the recording instrument marker field for a marker tip which can trace in extremely close proximity to another marker tip. In addition, there is a need for such a marker tip which produces a constant width trace, adapted to be read electronically (such as by electroscanning).
One effort to solve the problem, encountered with existing recorder instrument marker tips, of close proximity tracing is shown in U.S. Pat. No. 4,024,547 (Raahauge). Interference between adjacent markers, in close proximity passage, according to the Raahauge disclosure, involves angular disposition of adjacent pens and a relatively short nib shank. This may lead to the undesirable result of excessive ink evaporation through the extended exposed nib.
Thus, it is an object of the present invention to provide a recording instrument disposable marker tip with a nib shank which supports and protects the nib and which is shaped in such a manner as to allow tracing within a distance less than the diameter of a nib shank between trace lines (or less than 1/2 of the sum of the two nib shank diameters if the nib shanks have different diameters). A further object is to provide such a marker with minimum exposure of the nib surface to the air, to avoid evaporative ink loss through the exposed nib.
A still further object is to provide close proximity tracing markers adapted to lay down a constant width trace line independent of the angle at which the nib approaches the writing surface.
These and other objects are met by a disposable marker tip design which includes a tubular nib shank cut away (or molded as if it were cut away) in such a manner as to avoid interference with another proximate nib shank. In particular, the lower extremity of the nib shank is cut away on the side of a proximate and angularly disposed adjacent nib and nib shank. The nib shanks otherwise surround and support the writing nibs which generally draw ink from a capillary reservoir and make contact with the writing surface.
In accordance with a separate feature of the invention, the writing nib has a spherical tip which gives a constant width trace line independent of the angle at which the nib approaches the writing surface. Still further, adjacent nibs may be of different cross-sectional sizes, a longer nib having a larger cross section than a shorter nib, so as to enhance ink flow through the nib with a longer ink path, while a smaller cross section nib permits closer passing distance.
The configuration of the cut away of the lower nib shank may take any of various forms. In general, it is preferred not to cut away the shank unnecessarily since this impairs structural support and enchances evaporative ink loss from the nib.
The cut away configuration of a particular nib shank may include a planar cut of the shank at an angle between a plane perpendicular to the nib axis and a plane parallel to the nib axis. At the latter extreme, the cut is preferably along a tangent surface of the nib, facing the adjacent nib and is met by a return cut inward from the outer shank edge.
For a better understanding of the marker tip of the present invention, reference may be made to the drawings accompanying and forming a part of this specification. In the drawings like reference characters designate the same or similar parts in various views.